Analytical model of the mean velocity distribution in an open channel with double-layered rigid vegetation |
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| Institution: | 1. Faculty of Civil Engineering and Geosciences, Delft University of Technology, PO Box 5048, 2600GA Delft, The Netherlands;2. Pontificia Universidad Javeriana, Cra. 7 No. 40-62, Bogotá D.C., Colombia;3. Department of Water Engineering, UNESCO-IHE, PO Box 3015, 2601DA Delft, The Netherlands;4. Department of Civil and Environmental Engineering, University of Florence, P.zza S.Marco, 4 - 50121 Florence, Italy |
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| Abstract: | An analytical model for predicting the vertical distribution of mean streamwise velocity in an open channel with double-layered rigid vegetation is proposed. The double-layered model was constructed in a laboratory flume with an array of steel cylinders of two heights. For each vegetation layer (i.e., the short- or tall-vegetation layer), the flow is vertically separated into a lower vegetation zone and an upper vegetation zone, and corresponding momentum equations for each zone are formulated. For the lower vegetation zone, a uniform velocity was adopted since turbulent shear is relatively small and the Reynolds stress is ignored. For the upper vegetation zone, a power series was used to solve the momentum equations. For the free-water zone, a new expression was suggested to obtain a zero velocity gradient at the water surface instead of the traditional logarithmic velocity distribution. Good agreement between the analytical predictions and experimental data demonstrated the validity of the model. |
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| Keywords: | Double-layer model Vegetated flow Velocity distribution Power-series solution Mixing-length theory |
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